Monday, March 30, 2009
DNA Record
On page 66, Carroll talks about how by examining DNA we can study the evolution changes in different species. Explain the details of this technology and discuss the science knowledge needed to do this type of experiment. Furthermore, explain the techniques used to determine how a species has evolved over time. Finally, discuss how technological advancement may or may not better the accuracy of DNA studies.
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To examine DNA there are many options like using PCR, recombinant DNA technology, DNA fingerprinting, gene therapy, DNA microarray technology, and DNA profiling. All of these have allowed for breakthrough in medicine, forensic science, environmental science and national security. PCR or polymerase chain reaction, is the amplification of a sequence of DNA so scientists can study that strand of DNA. Then recombinant DNA became available for genetic engineering. Recombinant DNA is DNA that has been altered using bacterial restriction enzymes that cut the DNA creating sticky ends to bind to each other and then be inserted into another DNA. Also gene therapy is used to deliver corrected genes into people with defective genes in order to help them cure or fight a disease. To do any of these DNA procedures, DNA is simply needed even a small piece that can be amplified and then replicated to produce more DNA. In addition, enzymes are needed to cut the DNA and then to multiply it.
ReplyDeleteTo see if a species has evolved over time, a scientist would simply look at the DNA of that species and trace its patterns back to earlier recordings and history of that species. In addition, to see if evolution has occurred one can look for mutations in the DNA sequence which can only occur over time or through evolution.
Technological advancements in DNA studies have greatly improved the accuracy in all of the areas that it is currently being used for. For instance, DNA fingerprinting in law enforcement is only about 15 years old and has helped to convict or find innocent many people. Also, today smaller and smaller fragments of DNA can be used to do DNA fingerprinting because of the technology to multiply those small DNA fragments. Because of this new ability to take even semen and find the rapist is all due to advances in DNA technology and being able to grow and multiply DNA fragments with a high percentage of being accurate.
http://www.cjjohns.com/lawpowerandjustice/commentaries/Advance_DNA.html
http://science.jrank.org/pages/2134/DNA-Technology.html
http://en.wikipedia.org/wiki/Human_evolution
As Jackie Fisher stated above, gene cloning, recombinant DNA technology, PCR, electrophoresis, Southern Hybridization, DNA microarray assays, DNA profiling and various methods of DNA sequencing are only a few of the new, emerging DNA technologies that allow the close study of evolution and also benefit society.
ReplyDeleteOverall, the tracing of evolution in different species depend on first the knowledge of what that particular species’ DNA comprises of. Then, focusing on certain aspects of this information, such as the possible sites of mutation that would lead to that species’ diversity and variation or genetic similarities between relative species to complement the process of evolution, scientists can better understand the lineage of the evolutionary process. New DNA mapping and sequencing methods have allowed the development of entire organism genomes and new ways to further proteomics (the systematic study of the full protein sets) which will aid in tracing how selective adaptations have evolved at the molecular level. There are two main methods of DNA mapping that have developed over the years. The first method to develop was the hierarchical, three-stage approach. Due to the discovery of restriction fragment length polymorphisms, (RFLPs) scientists could create genetic markers throughout an organism’s genome. These loci of genetic differences could be sights of interests and a framework of organization of the genome and allow the creation of a linkage map along with microsatellites. Once a linkage map is established with different genetic markers throughout the chromosomes, large fragments of DNA are cut with different restriction enzymes. The idea revolves around chromosome walking so that similar sets of DNA fragments cut from different restriction enzymes overlap to create one cohesive, flowing sequence in correct order. Once the fragments are created, yeast artificial chromosome (YAC) or bacterial artificial chromosome (BAC) is used to clone numerous copies of the DNA fragments as these two vectors can receive long fragments of DNA. Then smaller fragments are created from the longer fragments, cloned and so forth until fragments with the length of 1,000 base pairs long are sequence with perhaps the Sanger method. The Sanger method comprises of synthesizing DNA strands with the random incorporation of a dideoxyribonucleotide that terminates the synthesis of the DNA strand because it lacks the -OH necessary for the binding of the next base. Several DNA fragments are used and for each of the four bases to create every possible location of that particular base. Then the information is combined to create the entire DNA fragment. Then with overlapping portions of DNA, the entire genome can be placed together like a puzzle.
The combination of these new technologies and techniques allowed the development of full genomes that could further dissected and each component studied to explore possible evolutionary processes. With DNA microarray assays, scientists could study gene expressions of certain genes of interest in the genome of a certain organism and discover which genes code for a particular protein. This is done by isolating mRNA, using reverse transcription, hybridizing the DNA, and then allowing numerous short single-stranded DNA molecule to bind with the targeted cDNA. This technology allows the scientist to fully understand how certain genes express a protein of interest that operates to create a distinctive property in the organism. Then through similarities and matching, relative species can be determined and further trace the development of these certain genes of interest between different species. On page 66 Sean Carroll describes how certain genetic variation can be differently favored in different environments and the continuation of that variation is then cemented with its survival. Understanding this, comparing how a gene has developed between similar species to establish kinship and the evolutionary process by studying the DNA record.
Using humans as an example, another way that DNA mapping can help trace evolution and the selecting choosing of certain advantages is the sequencing of single nucleotide polymorphisms. These SNPs are the primary sites of genetic mutation and variation in humans. As stated above, sequencing and studying these differentiating sites will help determine the evolutionary process in humans. Discovering what genetic sites constitute the majority of genetic variation and mutation in certain organisms will help in creating lineages and tracing the evolutionary process.
Overall the emergence of new DNA technologies has greatly furthered the studies of evolution and DNA in general, especially in the last few decades. The combination of these new cloning, sequencing, profiling, and organizing methods have allowed the mapping of entire genomes and the furthering of evolutionary studying.
http://science.jrank.org/pages/2134/DNA-Technology.html
http://en.wikipedia.org/wiki/Recombinant_DNA
Biology Campbell Reece